This is the first edition of Blackstone's Commentaries on the Laws of England Volume I.
Blackstone's four volume analysis of English common law proved to be even more popular in America than in England. Published just before the Revolutionary war, it immensely influenced the writers of the federal constitution.
From the time the Commentaries was published till the early 1900s these four volumes were required reading for all law students. Even now, it is still often cited by the Supreme Court.